Kinetics of EDTA-catalyzed oxidation of Indigo Carmine by vanadium(V)

The reaction is first order both in vanadium(V) and substrate and is markedly inhibited by H⁺ ions. Kinetic evidence for the formation of a 11 complex of vanadium(V) and EDTA is obtained. The stability constant of this complex and its thermodynamic parameters were evaluated. A suitable mechanism is proposed.

---

(V), H⁺. 11 (V) . . .

     

Catalytic properties and phase composition of multicomponent catalysts for oxidative ammonolysis of propane

Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.

---

. , ; , .

     

New substrates in Belousov-Zhabotinsky reaction employing mixed media

Several substrates have been employed in different oscillatory systems. A serious limitation is the low solubility in water. This has been overcome by employing aqueous-organic mixed media in the iodate-system as well as the uncatalyzed and catalyzed [Ce(III) or Ferroin] systems. The present paper deals with the study of fifteen new substrates in the bromate-Mn(II) oscillatory system employing aqueous-organic mixed media.

---

. . , - , (Ce(III) ), . -Mn(II) - .

     

Le systeme eau-theophylline

The binary system water—theophylline was studied by DTA and radiocrystallography. The slow dehydration of theophylline monohydrate was observed at room temperature at relative humidities lower than 60%, without the formation of any other hydrate. The isochoric phase diagram was established. At 78 °C, a peritectic invariant occurred, owing to decomposition of the monohydrate. The existence of only one binary compound (theophylline H₂O) was confirmed by the.Tammann diagram.

---

Zusammenfassung Mittels DTA und Radiokristallographie wurde das binäre System Wasser-Theophyllin untersucht. Bei einer relativen Luftfeuchtigkeit unter 60% wird bei Raumtemperatur eine langsame Dehydratation von Theophyllinemonohydrat ohne Formung anderer Hydrate beobachtet. Es wurde ein isochores Phasendiagramm entwickelt. Wegen der Zersetzung des Monohydrates tritt bei 78 °C eine peritektische Invariantheit auf. Die Existenz nur einer binären Verbindung (Theophyllin, H₂O) wird mittels eines Tammanndiagrammes bekräftigt.

---

— . 60% - . . 78° , . -.

     

Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

The thermal stability of alkaline earth metal hydrofluorides was studied by means of a Derivatograph. The values of the activation energy, reaction order and rate constant were determined. The comparison of the kinetic parameters of the decomposition process for the complete series of hydrofluorides studied led to a certain regularity in the differences in their thermal stabilities and its correlation with the strength of the hydrogen bond in their structure.

---

Zusammenfassung Die thermische Stabilität von Erdalkalihydrofluoriden wurde mit Hilfe eines Derivatographen untersucht, die Werte der Aktivierungsenergien, der Reaktionsordnung und der Geschwindigkeitskonstanten bestimmt. Der Vergleich der kinetischen Parameter des Zersetzungsvorganges wies auf eine gewisse Regelmäßigkeit in ihrer verschiedenen thermischen Stabilität, die in Zusammenhang mit der Stärke ihrer strukturalen Wasserstoffbindung steht.

---

Résumé On a étudié la stabilité thermique des hydrogénofluorures des métáux alcalinoterreux et déterminé les valeurs des énergies d'activation, des ordres de réaction et des constantes de vitesse de réaction à l'aide d'un Dérivatographe. Après comparaison des paramètres cinétiques on a pu établir une certaine régularité dans le changement de la stabilité thermique en corrélation avec la force de liaison de l'hydrogène dans la structure.

---

. , . .

     

Catalytic properties of nickel oxide and its solid solutions in magnesium oxide in hydrogen oxidation

Temperature dependence of the reaction rate of H₂ oxidation on nickel oxide and solid solutions of nickel ions in MgO prepared at 573–1373 K, has been studied. The variation of the catalytic properties with temperature is attributed to the presence of nickel ions in different oxidation states simultaneously, i. e. Ni(II) and Ni(III).

---

H₂ MgO, 573–1373 K. — Ni(II) Ni(III).

     

Oxidation of ethylene to ethylene oxide: A tpr study on fresh and aged catalysts

The deactivation of a silver catalyst was investigated after six years of industrial production of ethylene oxide. Temperature-programmed reduction was used to characterize the chemical nature of the silver and its reactivity towards oxygen. The fresh and some aged catalysts were examined, also after different thermal treatments.During the industrial run, the surface species were modified and some oxygen diffused into the bulk of the metal. Aging caused permanent changes in the characteristics of the silver, resulting in a different interaction with oxygen. The TPR spectra exhibited a trend along the reactor axis, suggesting a correlation with the degree of deactivation of the catalyst.

---

Zusammenfassung Die Desaktivierung eines Silberkatalysators wurde nach 6-jährigem Einsatz zur industriellen Produktion untersucht. Temperaturprogrammierte Reduktion wurde angewandt, um die chemische Natur des Silbers und dessen Reaktivität gegenüber Sauerstoff zu charakterisieren. Frische und einige gealterte Katalysatoren wurden nach verschiedenen thermischen Vorbehandlungen untersucht. Die Alterung verursachte bleibende Veränderungen in charakteristischen Eigenschaften des Silbers, was in der unterschiedlichen Wechselwirkung mit Sauerstoff zum Ausdruck kommt. Die TPR-Resultate zeigen einen Trend entlang der Reaktorachse, was auf eine Korrelation mit dem Grad der Desaktivierung des Katalysators hindeutet.

---

. () . , , . . , , . , .

---

---

The experimental contributions by F. Genoni and G. Valassina are gratefully acknowledged.     

Mechanism of ring expansion in 1-ethylindane under dehydrogenation conditions

Studies of 1-ethyl-(-¹⁴C)-indane dehydroisomerization over a Pt/Al₂O₃ catalyst (AP-64) have revealed that 34.5% or 16.5% of the initial tracer label migrates into the -position of the expanded methylnaphthalene ring when the catalyst is pretreated at 763 K in Ar or H₂, respectively. The reaction mechanism is discussed.

---

1--(¹⁴C)- -64. , 763 - 34,5% , —16,5%. .

     

ESR studies of Mo?Mg oxide catalysts

For 0.1–0.5 wt.% Mo–Mg oxide samples with high concentration of⁹⁵Mo isotopes two types of Mo⁵⁺ have been identified. Their role in the formation of O ₂ ^– anion-radicals in low-temperature oxygen adsorption on reduced samples has been established.

---

, ⁹⁵Mo, Mo⁵⁺ Mo–Mg (0,1–0,5 .% Mo) - O ₂ ^– .

     

Catalytic oxidation of acrolein to acrylic acid over a molybdenum-vanadium catalyst

By the method of gas chromatography it has been found that the adsorption of acrolein takes place without dissociation whereas acrylic acid is adsorbed dissociatively. The adsorption of water vapor proceeds also dissociatively and results in increasing the number of the Brönsted acid centers. The presence of water vapor has a positive effect on the desorption rate of acrylic acid and a negative effect on the reoxidation rate of the catalyst.

---

, , . , . , — .